diff --git a/cmake_targets/tools/build_helper b/cmake_targets/tools/build_helper
index dab36592e3221784bff2967d86e9c97c52714a7a..9234358babc5dd98d4b49bc4170d058e946c76b8 100755
--- a/cmake_targets/tools/build_helper
+++ b/cmake_targets/tools/build_helper
@@ -345,16 +345,20 @@ install_asn1c_from_source(){
 ################################################
 
 install_nas_tools() {
-    cd $1
-    if [ ! -f .ue.nvram ]; then
-        echo_success "generate .ue_emm.nvram .ue.nvram"
-        ./nvram --gen
-    fi
+  cd $1
+  if [ ! -f .ue.nvram ]; then
+    echo_success "generate .ue_emm.nvram .ue.nvram"
+    ./nvram --gen
+  else
+    [ ./nvram -nt .ue.nvram  -o ./nvram -nt .ue_emm.nvram] && ./nvram --gen
+  fi
 
-    if [ ! -f .usim.nvram ]; then
-        echo_success "generate .usim.nvram"
-        ./usim --gen
-    fi
+  if [ ! -f .usim.nvram ]; then
+    echo_success "generate .usim.nvram"
+    ./usim --gen
+  else
+    [ ./usim -nt .usim.nvram ] && ./usim --gen
+  fi
 
 }